JP2001099204A - Dynamo-electric disc brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately detect a contact position of a brake pad to a disc rotor. SOLUTION: A ball lamp mechanism 27 is driven by a motor 12 to press brake pads 6, 7 against a disc rotor 2 by means of a piston to generate a braking force. A relative position between a piston 28 and a movable disc 33 of the mechanism 27 is controlled according to wear of the pads 6, 7 by a pad wear compensation mechanism composed of a limitter part 30 and a screw part 48 to thereby compensate the wear of the pads 6, 7. Upon start-up of brake system of an electric disc brake 1, the motor 12 is rotated in the direction to retreat the piston 28 to thereby moving the mechanism 27 to a termination position, and based on the termination position, the pad contact position is determined. Accordingly, determination of accurate pad contact position can be attained without being influenced by change in temperature as well as the wear of pad.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric disc brake device for generating a braking force by the rotation of an electric motor.

[0002]

2. Description of the Related Art A so-called "dry brake" in which a braking force is generated by the output of an electric motor without using a brake fluid as a braking device for a vehicle such as an automobile.
Devices are known.

[0003] As a dry brake device, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-206766, the rotational motion of an electric motor is converted into advance and retreat of a piston by a ball screw mechanism, and a brake pad is disc-shaped by the piston. There is an electric disc brake device that generates a braking force by being pressed by a rotor. In this type of electric disc brake device, a brake pedal depression force (or displacement amount) by a driver is detected by a sensor, and a controller controls the rotation of the electric motor according to the detection to obtain a desired braking force. I have to.

Further, in the above-described electric disc brake device, various sensors are used to detect the vehicle state such as the rotation speed of each wheel, the vehicle speed, the vehicle acceleration, the steering angle, the vehicle lateral acceleration, etc. By controlling the rotation of the electric motor based on these detections, boost control, antilock control, traction control, vehicle stabilization control, and the like can be relatively easily incorporated.

[0005] In this type of electric disc brake device,
In order to control braking force and pad clearance, etc.
It is necessary to detect the pad contact position where the brake pad contacts the disk rotor. Conventionally, when detecting the pad contact position at the time of starting the control device, the motor is rotated,
The piston is advanced, and the brake pad is actually brought into contact with the disk rotor to detect the pad contact position.

[0006]

However, in the above-mentioned conventional electric disc brake device for detecting the pad contact position by bringing the brake pad into contact with the disc rotor,
There were the following problems. In such an electric disc brake device, a pad contact position is detected by detecting a change in load when a brake pad comes into contact with a disc rotor as a change in resistance of the motor, that is, a change in current. Relationship between the current and the motor position of the motor is as shown in FIG. 5, it is possible to detect the pad contacting points by detecting the motor position p ₀ to the current I ₀ starts changing to the motor. However, it is difficult to detect the point at which the current I ₀ starts to change due to the influence of noise or the like. Therefore, actually, the current I ₁ at the point p ₁ further moved by a certain amount Δx from the pad contact position is detected. and, so as to obtain the motor position p ₀ of the pad contact points on the basis of the current I _1.

However, the rigidity of the brake caliper, which determines the relationship between the load on the motor and the motor position, greatly changes depending on the temperature, the amount of pad wear, and the like. If the relationship becomes as indicated by a broken line in FIG. 5, the current I ₁
In this case, the actual motor position becomes p ₂ , and the motor position at the pad contact point cannot be obtained accurately.

The present invention has been made in view of the above points, and has as its object to provide an electric disc brake capable of accurately detecting a reference position of a brake pad.

[0009]

In order to solve the above-mentioned problems, the present invention provides a pair of brake pads arranged on both sides of a disk rotor, a piston for pressing the brake pads, an electric motor, and the electric motor. An electric disc brake, comprising: a ball ramp mechanism for converting a rotational motion of a motor into a linear motion to advance and retreat the piston; and a pad wear compensation mechanism for advancing the piston in accordance with wear of the brake pad. Rotating the electric motor in a direction to retract the ball ramp mechanism to a terminal position, and determining a pad contact position where the brake pad contacts the disk rotor based on the terminal position. I do.

[0010] With this configuration, the initial position of the electric motor can be accurately positioned by moving the ball ramp mechanism to the terminal position, and the pad contact position can be determined based on the position. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the electric disc brake 1 of the present embodiment has a caliper body 3 disposed on one side (usually inside the vehicle body) of a disc rotor 2 that rotates with wheels (not shown). The caliper body 3 has a claw portion 4 formed in a substantially C shape and extending to the opposite side across the disk rotor 2 by a bolt (not shown).
Are connected together. Brake pads 6 and 7 are provided on both sides of the disk rotor 2, that is, between the disk rotor 2 and the caliper body 3 and between the tip of the claw portion 4. Brake pads 6, 7
Is supported movably along the axial direction of the disk rotor 2 by a carrier 8 fixed to the vehicle body, so that the braking torque is received by the carrier 8. It is slidably guided along the axial direction of the disk rotor 2 by an attached slide pin (not shown).

A substantially cylindrical case 11 of the caliper body 3 to which an annular flange 10 formed at the base of the claw 4 is connected.
Inside, an electric motor 12 and a rotation detector 13 are provided,
The ball lamp unit 14 is an annular flange 10 of the claw 4
It is inserted into the rotor 15 of the electric motor 12 from the side. A cover 16 is attached to the rear end of the case 11 by bolts (not shown).

The electric motor 12 has a stator 18 fixed to the inner peripheral portion of the case 11 and slides on the case 11 so as to face the inner peripheral portion of the stator 18 by means of sliding bearings 19 and 20 and is movable in the axial direction. And a rotor 15 supported as possible.
The rotation detector 13 has a resolver stator 23 fixed to a resolver case 22 attached to the case 11 by bolts 21.
And a resolver rotor 24 fixed to the rotor 15 so as to face the resolver stator 23, and detects the rotational position of the rotor 15 based on their relative rotation.

The cover 16 is provided with a connector 25 and a cable 26 connected to the electric motor 12 and the rotation detector 13. The electric motor 12 is provided with a control signal (electric signal) from a controller (not shown). , The rotor 15 can be rotated by a desired angle with a desired torque. The connector 25 and the cable 26 are inclined with respect to the axial direction of the disk rotor 2 and extend radially outward to avoid interference with members such as arms, links, knuckles, and struts of the suspension device of the vehicle. Have been.

The ball lamp unit 14 includes an electric motor 12
A ball ramp mechanism 27 that converts the rotational movement of the rotor 15 into a linear movement, and a piston 28 that presses the brake pad 6
And an adjustment nut 29 interposed therebetween, and a limiter mechanism 30 (pad wear compensation mechanism) for transmitting the rotation of the ball ramp mechanism 27 to the adjustment nut 29.

The ball ramp mechanism 27 is in contact with the flange portion 10 of the claw portion 4 and is fixed by a pin 31 so as not to rotate, and an movable fixed disk 32 disposed opposite the fixed disk 32. And a ball 34 (steel ball) interposed between them. The movable disk 33 is integrally formed with a cylindrical portion 35 that is inserted into the fixed disk 32 and extends to the inside of the case 11. Cylindrical part
35 is spline-coupled to the inner periphery of the rotor 15,
These spline connection portions 36 are provided with appropriate play in the rotation direction and the radial direction in consideration of the slidability in the axial direction, the dimensional tolerance, and the assemblability.

On the opposing surfaces of the fixed disk 32 and the movable disk 33, three ball grooves 37 and 38 are formed, each extending in an arc along the circumferential direction. These ball grooves 37 and 38 have the same central angle (for example, 90 degrees).
°) and are arranged at equal intervals. The ball grooves 37 and 38 are each inclined in the same direction,
The balls 34 are inserted between the ball grooves 37 and 38, and the three balls 34 roll in the ball grooves 37 and 38 by the rotation of the movable disk 33 with respect to the fixed disk 32, and are movable according to the rotation angle. The disk 33 moves in the axial direction in a direction away from the fixed disk 32.

The adjusting nut 29 comprises a cylindrical portion 39a and a flange portion 39b formed outside one end of the cylindrical portion 39a. The cylindrical portion 39a is inserted through the cylindrical portion 35 of the movable disk 33 and is rotatably supported by a slide bearing 40. The flange 39b is in contact with one end of the movable disk 33 and is rotatably supported by a thrust bearing 41. Cylindrical part 39 of adjustment nut 29
The “a” is extended to the inside of the rotor 15 in the case 11, and a limiter mechanism 30 is mounted on an outer periphery of a tip portion thereof.

The limiter mechanism 30 includes a cylindrical portion of the adjustment nut 29.
Limiter 42 and spring holder on the outer periphery of the tip of 39a
43 are rotatably fitted on the outside, and these are coil springs 44
Are connected to each other. The limiter 42 and the spring holder 43 are engaged with each other so that they can rotate relative to each other within a predetermined range, and a predetermined set load is applied to the rotation direction by the coil spring 44.
Can be rotated clockwise (clockwise when viewed from the left in FIG. 1; the same applies hereinafter) against the set load of the coil spring 44 with respect to the spring holder 43. An engagement concave portion 45 formed in the limiter 42 is engaged with an engagement convex portion 46 formed at an end of the cylindrical portion 35 of the movable disk 33,
The limiter 42 can rotate relative to the cylindrical portion 35 within a predetermined range. A clutch spring 47 (coil spring) is wound around the outer periphery of the tip of the cylindrical portion of the adjustment nut 29, and one end of the clutch spring 47 is connected to a spring holder 43.
The clutch spring 47 acts as a one-way clutch by expanding and reducing the diameter by torsion, so that only the clockwise rotation of the spring holder 43 is transmitted to the cylindrical portion 39a of the adjustment nut 29. Has become.

The piston 28 is screwed into a thread portion 48 (pad wear compensation mechanism) formed on the inner peripheral portion of the adjustment nut 29. When the adjustment nut 29 rotates clockwise with respect to the piston 28, the brake pad 6 is rotated. It moves forward to the side. In the cylindrical portion 39a of the adjustment nut 29, a detent rod 50, one end of which is fixed to the resolver case 22 by a nut 49, is inserted, and the other end of the detent rod 50 can slide on the piston 28 in the axial direction. And is engaged so as to restrict rotation. A detent cap 28b is attached to the rear end of the piston 28 so as to restrict the relative rotation between the detent rod 50 and the piston 28 and to allow relative axial movement. Flange part 51 formed in the middle part of detent rod 50 and cylindrical part of adjustment nut 29
A plurality of disc springs 53 are interposed between the flange portion 52 formed in the inside 39a and the adjusting nut by the spring force.
29 is biased to the right in FIG. And nut 49
By moving the axial position of the non-rotating rod 50, the urging force (set load of the disc spring 53) on the adjustment nut 29 can be adjusted.

A substantially cylindrical case 54 is attached to the fixed disk 32, the movable disk 33 and the adjustment nut 29 of the ball ramp mechanism 27 so as to cover the outer periphery of these flange portions. The case 54 has a flange portion 55 formed inside a tapered front end portion, and an engagement claw 56 having a notch formed inside a cylindrical rear end portion. And fixed disk
32 is engaged with the engaging claw 56, and the flange 55 and the adjusting nut 29 are
A wave washer 57 is interposed between the fixed disc 32, the movable disc 33 and the ball 34.
And the elasticity of the wave washer 57 allows the movable disk and the adjustment nut 29 to move in the axial direction, and provides a moderate resistance to the rotation of the adjustment nut. The tip of a piston boot 58 attached to the flange 55 is connected to the outer periphery of the tip of the piston 28 attached to the adjustment nut 29. The cylindrical portion of the case 54 is fitted to the claw portion 4, and the space therebetween is sealed by an O-ring 59.

Next, the normal operation of the electric disc brake 1 will be described. At the time of braking, when the rotor 15 of the electric motor 12 rotates clockwise with a predetermined torque in response to a signal from a controller (not shown), the spline coupling portion is
The movable disk 33 of the ball ramp mechanism 27 is rotated via 36, and the ball 34 rolls along the ball grooves 37 and 38 to advance the movable disk 33 toward the brake pad 6 along the axial direction. This thrust is applied to the adjustment nut 29 via the thrust bearing 41.
Is transmitted to the piston 28 via the screw portion 48, and the one brake pad 6 is
The caliper body 3 moves along the slide pin of the carrier 8 by the reaction force, and the claw 4 presses the other brake pad 7 against the disk rotor 2, and is controlled according to the torque of the electric motor 12. Power is generated.

When the braking is released, the electric motor 12 is rotated in the reverse direction, and the movable disc 33 is rotated counterclockwise to the original position, and the movable disc 33, the adjusting nut 29 and the piston 28 are retracted by the spring force of the disc spring 53. And caliper body 3
Moves along the slide pins of the carrier 8, the brake pads 6, 7 are separated from the disk rotor 2, and the braking is released.

Next, compensation of wear of the brake pads 6 and 7 will be described. If there is no wear on the brake pads 6 and 7, or after the wear adjustment described below has been performed,
At the time of braking, when the piston 28 advances from the non-braking position by a predetermined pad clearance due to the rotation of the rotor 15 and the brake pads 6 and 7 move to the braking start position (pad contact position) where they come into contact with the disk rotor 2, the movable disk
The engagement protrusion 46 of the cylindrical portion 35 of the 33 and the engagement recess 45 of the limiter 42 rotate relative to each other within a predetermined range. Further, when the movable disk 33 rotates while pressing the brake pads 6 and 7 against the disk rotor 2, the engaging projection 46 rotates the limiter 42 clockwise, and the rotational force is transmitted via the coil spring 44 and the clutch spring 47. Is transmitted to the adjustment nut 29, but the piston 28 presses the brake pad 5,
Since a large frictional force is generated in the screw portion 48 between the piston 28 and the adjustment nut 29, the coil spring 44 is bent and the adjustment nut 29 does not rotate.

Thereafter, when the piston 28 retreats by a predetermined pad clearance due to the reverse rotation of the movable disk 33 when the braking is released, the engaging projection 46 abuts against one end of the engaging recess 45 to limit the limiter 62 and the spring. Although the holder 43 is rotated counterclockwise, the piston 28 does not rotate because the clutch spring 47 expands in diameter and idles. In this way, pad wear is not adjusted and constant pad clearance is maintained.

When the brake pads 6, 7 are worn, during braking, the brake pads 6, 7 are moved from the non-braking position by the above-mentioned predetermined pad clearance by the clockwise rotation of the rotor 15, and the engagement protrusions are formed. Even if the portion 46 and the engaging recess 45 rotate relative to each other within a predetermined range, the brake pads 6 and 7 do not contact the disk rotor 2 due to the wear. When the rotor 15 further rotates, the movable disk 33 and the adjustment nut 29 advance to the disk rotor 2 side, and the piston 28 brings the brake pads 6 and 7 into contact with the disk rotor 2. At this time, the engaging projection 46 rotates the limiter 42 clockwise, and the rotational force is transmitted to the adjustment nut 29 via the coil spring 44 and the clutch spring 47.
The piston 28 does not press the brake pads 6 and 7,
Since a large frictional force is not generated in the screw portion 48 between the piston 28 and the adjustment nut 29, the adjustment nut 29 rotates clockwise to further advance the piston 28 toward the brake pads 6 and 7, thereby causing wear of the pad. To adjust. When the brake pads 6 and 7 press the disk rotor 2, the piston
A large frictional force is generated in the screw portion 48 between the nut 28 and the adjustment nut 29, and the coil spring 44 is bent, so that the rotation of the adjustment nut 29 is stopped.

Thereafter, at the time of braking release, when the piston 28 retreats by a predetermined pad clearance due to the counterclockwise rotation of the rotor 15, the engaging projection 46 contacts one end of the engaging recess 45, and the limiter 42 is released. Although rotated counterclockwise, the adjustment nut 29 does not rotate because the clutch spring 47 expands in diameter and runs idle. In this way, the piston 28 is moved from the adjustment nut 29 to the brake pads 6, 7 for each operation of braking and braking against wear of the brake pads 6, 7.
By advancing appropriately to the side 7 and repeating this, the wear adjustment of the brake pads 6 and 7 can be automatically performed.

Next, a method of detecting a pad contact position where the brake pads 6 and 7 contact the disk rotor when the control system of the electric disk brake 1 is started or the like will be described with reference to FIGS.

The operation will be described with reference to the flowchart of FIG.
First, in a step, it is determined whether or not it is necessary to detect a pad contact position (initial position). Normally, it is necessary to detect the pad contact position as an initial setting when the control system is started.

When it is necessary to detect the pad contact position, the electric motor 12 is moved in the step of retracting the piston 28 in a step.
By rotating the rotor 15 of FIG. 2, the movable disk 33 of the ball ramp mechanism 27 at an arbitrary position is rotated as shown in FIG. 2, and the ball 34 is moved to the fixed disk 32 and the movable disk 33 as shown in FIG. The movable disk 33 is moved to an end position where the rotation of the movable disk 33 to one side is restricted by contacting the ends of the grooves 37 and 38.

In the step, it is determined that the ball ramp mechanism 27 has moved to its end position. Ball ramp mechanism 27
Since the load on the electric motor 12 increases at the terminal position and its electric resistance increases, the terminal position can be detected by monitoring the current to the motor. For example, as shown in FIG. 5, in the end position p _e, the resistance or current of the electric motor 12 by the increase in the load increases, it is possible to detect the end position with a predetermined detection current I ₂ after increasing . Alternatively, the terminal position may be detected after a predetermined time has elapsed after the electric motor 12 starts rotating. Thus, the ball ramp mechanism
27 end positions can be easily detected.

When the end position is detected, the electric motor 12 is stopped in a step. By moving the ball ramp mechanism 27 to the end position, the initial position of the rotor 15 of the electric motor 12 can be accurately set, and the displacement between the grooves 37 and 38 of the ball ramp mechanism 27 and the ball 37 is corrected. can do.

Next, in a step, the ball ramp mechanism 27
The motor position corresponding to the pad contact position where the brake pads 6 and 7 contact the disk rotor 2 is obtained based on the end position of the brake pad. Since the distance between the movable disk 33 of the ball ramp mechanism 27 and the friction surfaces of the brake pads 6 and 7 is constantly adjusted by the pad wear compensation mechanism, the pad contact position is determined based on the end position of the ball ramp mechanism 27. It can be easily determined.

Then, the electric motor 12 is rotated at a step so that a predetermined pad clearance is obtained between the disk rotor 2 and the brake pads 6 and 7 based on the pad contact position determined at the step. Advance 28.

In this way, by rotating the electric motor 12 in the reverse direction and moving the ball ramp mechanism 27 to the end position, the pad contact position can be easily determined, and the brake pads 6, 7 can be accurately positioned. can do. Since the end position of the ball ramp mechanism 27 is hardly affected by a change in the rigidity of the brake caliper due to a change in temperature or wear of the brake pads 6 and 7, the pad contact position can always be determined accurately.

Further, as shown in FIG. 4, the groove 37, 38 is deepened near the end position of the ball ramp mechanism 27 to increase the lamp angle, so that the electric motor is formed near the end position.
Even if the torque of 12 is reduced to zero, the ball 34 moves to the ends of the grooves 37 and 38 by the reaction force against the movable disk 33,
The ball ramp mechanism 27 can be moved to the terminal position. In this case, since the ramp angle near the end position is large, the responsiveness when starting from the end position with no load can be improved.

[0037]

As described in detail above, according to the electric disc brake of the present invention, the initial position of the electric motor can be accurately positioned by moving the ball ramp mechanism to the end position. The pad contact position can be determined based on the pad contact position. Since the end position of the ball ramp mechanism is hardly affected by a change in the rigidity of the brake caliper due to a change in temperature or wear of the brake pad, the pad contact position can always be determined accurately.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electric disc brake according to one embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a ball ramp mechanism in a normal operation state of the apparatus of FIG.

FIG. 3 is a conceptual diagram showing a ball ramp mechanism at an end position of the apparatus of FIG. 1;

FIG. 4 is a conceptual diagram showing a modified example of the ball ramp mechanism of the apparatus shown in FIG. 1 in which the ramp angle near the end is increased.

FIG. 5 is a diagram showing a relationship between a motor position and an electric current of an electric motor that drives a ball ramp mechanism of the apparatus shown in FIG.

FIG. 6 is a flowchart for determining a pad contact position of a disc brake according to an embodiment of the present invention.

[Explanation of symbols]

 1 Electric disc brake 2 Disc rotor 6,7 Brake pad 12 Electric motor 27 Ball ramp mechanism 28 Piston 30 Limiter mechanism (Pad wear compensation mechanism) 48 Screw (Pad wear compensation mechanism)

Claims (1)

[Claims] 1. A pair of brake pads disposed on both sides of a disk rotor, a piston pressing the brake pad, an electric motor, and a rotary motion of the electric motor converted into a linear motion to move the piston forward and backward. An electric disc brake comprising a ball ramp mechanism and a pad wear compensation mechanism for advancing the piston in accordance with wear of the brake pad, wherein the electric motor is rotated in a direction to retract the piston, and the ball ramp mechanism is rotated. An electric disc brake, wherein the brake pad is moved to a terminal position, and a pad contact position at which the brake pad contacts the disk rotor is determined based on the terminal position.